Hello CraigD
Doing run time you can use this following command:
GetDlgItem(ID_OF_BUTTON_HERE)->EnableWindow(TRUE)
This will of course enable the button. If you put in the Boolean value of FALSE in the EnableWindow(), it will disable it (dim it out so to speak). This command can be placed anywhere in your program where there is an event driven action, such as clicking a pushbutton, or a checkbox, etc, etc.
Hope this helps you out some.
Nyjil